Rail Assembly, Rail Switch And A Transport Device Provided With A Magnetostrictive Sensor

ABSTRACT

In order to detect a vehicle position on a rail assembly, magnetorestrictive sensors are integrated into said rail assembly and marking magnets are disposed on the vehicles. Measuring bars are successively arranged without overlapping each other, thereby forming a measuring path. In order to detect the vehicle position even in areas where the bars are jointed to each other, each vehicle is provided with at least two marking magnets which are arranged at a certain distance from each other. A rail switch provided with at least two measuring bars is also disclosed.

ACKNOWLEDGMENT OF RELATED APPLICATIONS

The present application claims the priority of Swiss patent application number 908/03, which was filed on 21 May 2003, and whose disclosure is hereby incorporated in its entirety into the present application by reference.

The present invention relates to a rail system, a switch, and a transport device having magnetostrictive sensors according to the preamble of the independent claims.

From WO 00/75603, a rail system for a packaging machine is known that is equipped with magnetostrictive sensors in order to measure the position of the vehicles. Each sensor has a measurement head and a measurement bar, and determines from a runtime delay the position of a marking magnet attached to the vehicle that operatively interacts with the measurement bar. For measurement along the entire rail system, a plurality of magnetostrictive sensors are provided whose measurement bars overlap at their ends.

In practice, it has turned out that such devices are expensive to manufacture and have only limited measurement precision. In addition, there is the problem that an arrangement of the sensors is desirable that is also suitable for switch areas.

Therefore, in a first aspect of the present invention the problem arises of providing a system of the type named above that is reliable and precise while being easy to manufacture.

This object is achieved by the rail system and the transport device according to the independent claims.

According to these claims, the measurement bars situated one after the other form at least one measurement path that runs along the rail system, in which the measurement bars do not overlap. This increases the measurement precision, or simplifies, with the same degree of precision, the construction and the calibration, because a lateral offset of the measurement bars is not required.

Preferably, at least two marking magnets are provided that are situated one after the other in the direction of travel. The marking magnets are situated in such a way that even during a transition from one measurement bar to the next, at least one marking magnet is always effectively connected to at least one of the measurement bars. In this case, the measurement control unit can also reliably determine the position of vehicles in the area of the transition.

The system of magnetostrictive sensors according to the present invention is advantageous in particular if the rail system has a multiplicity of rail elements situated one after the other, at least one measurement bar being situated in each rail element. Because no overlapping of the measurement bars is necessary, the construction and assembly of the rail elements is simplified.

In another aspect, the problem arises of providing a switch having a magnetostrictive measurement system. This object is achieved by the switch according to the independent claims.

The switch has, as is standard, a first, a second, and a third end, the rail system branching from the first end into the second and the third end. The switch has magnetostrictive sensors for measuring vehicle positions, each sensor having a measurement bar and a measurement head in order to detect, from a runtime delay, the position of a marking magnet situated on a vehicle. In the area of the switch, a measurement bar extends from the first to the second end and a measurement bar extends from the first to the third end. This makes it possible to precisely measure the position of the vehicles on both switch paths.

If a part of a drive device is integrated in the switch, such as for example the active part of a linear drive mechanism, the measurement bars are preferably situated laterally outside the drive device, so that these measurement bars do not cross one another, thus simplifying the construction.

Preferably, the vehicle is equipped with at least two marking magnets situated next to one another transverse to the direction of travel, so that, independent of the path traveled on the switch, at least one of the marking magnets is effectively connected to one of the measurement bars.

In the present application, the term “rail system” is understood as a guide system for a vehicle that can run in a straight line or in curved fashion, and/or can comprise at least one corner piece and/or at least one switch.

Additional preferred embodiments and applications of the present inventions result from the dependent claims, as well as from the following description based on the Figures.

FIG. 1 shows a side view of a transport device according to the present invention,

FIG. 2 shows a view from above of the transport device of FIG. 1,

FIG. 3 shows a section along the line III-III in FIG. 2,

FIG. 4 shows a detail from FIG. 3,

FIG. 5 shows a section along the line V-V of FIG. 2,

FIG. 6 shows a view of a switch from above, and

FIG. 7 shows a section through an alternative embodiment of a rail element.

The transport device shown in FIGS. 1 to 3 comprises a rail system 1 formed by a multiplicity of rail elements 2 situated one after the other. Each rail element 2 has a basic element 3, manufactured by casting, in which there are situated two guide rods 4, a magnetostrictive sensor 5 having a measurement bar 6 and measurement head 7, and coils 8 having laminated cores as an active part of a linear drive mechanism. The vehicle side of rail element 2 is covered by a stainless steel plate 9.

Vehicles 11 traveling on the rail system are made up of a plurality of vehicle parts 11 a, 11 b, connected to one another in hinged fashion, and each having two wheels 12. In addition, a total four marking magnets 13 are situated on each vehicle, two on each side. Before and/or after marking magnets 13, guide magnets 14 are fastened to vehicle 11. In addition, drive magnets 15 are situated on the lower side in the center of the vehicle that work together with coil 8 in order to drive vehicle 11 along the rail system.

Guide magnets 14 are situated vertically above guide rods 4. The latter are each made up of a U-shaped section whose limbs are oriented towards the railway and that extends along the longitudinal axis of the rail system and is made of a magnetizable material. In this context, “magnetizable” refers to ferromagnetic or paramagnetic materials that have a magnetic susceptibility much greater than 1 and that exert a strong attractive force on guide magnets 14.

As can be seen in FIG. 5, guide magnets 14 are polarized in such a way that different polls are situated over the two limbs of the respective guide rod 4, so that there is a magnetic lock through the U-shaped section.

Guide magnets 14 are dimensioned so as to produce an interaction with guide rods 4 that is sufficiently strong to hold the vehicle on rail system 1 even in curves. If guide magnets 14 are sufficiently strong, vehicles 11 can also be situated in suspended fashion.

The drive takes place via electronic controlling of coils 8 by means of a control unit 17, shown schematically in FIG. 2. Control unit 17 forms a control loop whose manipulated variable is the currents through the individual phases of coils 8 and whose regulating variable is the measured vehicle position. In other words, the currents through the coils of the control unit are selected in such a way that the vehicle travels or maintains a predetermined position (which can be time-dependent), the current position being determined using magnetostrictive sensors 5.

As already mentioned, each magnetostrictive sensor 5 has a measurement bar 6 that extends along the longitudinal direction of the rails. Preferably, measurement bar 6 is situated in the U-shaped section of one of the guide rods 4 (as shown in FIGS. 3 and 4), and runs lateral to coils 8 along the outer edge of rail system 1, as is shown in FIG. 2.

Measurement bar 6 is made of a magnetostrictive material. A current pulse flows through it at regular temporal intervals; this pulse interacts with the field of marking magnets 13 and produces an ultrasound pulse. The ultrasound pulse runs along the sensor bar and is detected in the respective measurement head 7. From the time delay between the current pulse and the detected ultrasound pulse, the position of marking magnet 13 can be inferred.

Magnetostrictive sensors of the type described here are offered for example by the company MTS Sensor Technology GmbH & Co. KG (Germany), under the trade name Temposonics®.

Preferably, each measurement bar 6 extends over only one rail element. However, it is also conceivable to use measurement bars 6 that extend over a plurality of rail elements. A combination of measurement bars having different lengths is also conceivable.

The measurement bars, which succeed one another in the longitudinal direction of the rails, are situated one after the other (i.e., without a lateral offset transverse to the longitudinal direction of the rails) without overlapping, and form a measurement path. The non-overlapping arrangement of measurement bars 6 makes it possible to integrate them fully into rail elements 2. However, this arrangement also has the result that zones 20 are present between rail elements 2 in which a marking magnet 13 cannot be acquired. Because, however, two marking magnets 13 are provided on each vehicle 11 per measurement bar 6, at a distance from one another that is greater than the length of zones 20, measurement control device 17 can nonetheless acquire a vehicle from at least one measurement bar 6 if the vehicle is situated in the area between two rail elements 2.

In a preferred embodiment, the measurement for example always takes place at the position of the front (in the travel direction of the vehicle) marking magnet, until the distance from the front marking magnet up to a front (in the travel direction) end of the measurement bar becomes less than a predetermined threshold value. When the threshold value has been undershot, the measurement takes place using the rear (in the direction of travel) marking magnet, until the front marking magnet reaches the measurement area of the next (in the direction of travel) measurement bar 6. The measurement of the position then takes place using the next measurement bar and the front marking magnet.

Stated generally, a marking magnet 13 is used for a measurement only when it is situated in a predetermined measurement area of one of the measurement bars. If the marking magnet 13 is not situated in the predetermined measurement area of one of the measurement bars, the second marking magnet, situated in front of or behind the respective marking magnet 13, is used for the measurement. If both marking magnets, situated one after the other, are situated in the measurement area of a measurement bar (or of two different measurement bars), either both of the marking magnets or only one of the marking magnets can be used for the measurement.

As already mentioned, marking magnets 13 are situated on both sides of each vehicle. As a rule, however, only a single measurement bar is integrated into rail elements 2, so that only two of the four marking magnets are used. However, the two additional marking magnets have the advantage that the vehicles can be placed onto the rail system in both possible orientations. Moreover, as is described below, they enable reliable acquisition of the position of the vehicles even at switches.

A switch 2 a is shown in FIG. 6. It has a first end 22, a second end 23 a, and a third end 23 b, first end 22 being capable of being optionally connected to second or third end 23 a or 23 b. Lateral control magnets 24, 25, which interact with guide magnets 14 of the vehicles, steer the vehicles in one direction or the other.

As is shown in broken lines, two measurement bars 6 are integrated into the switch, of which each runs parallel to and close to an outer edge 26, 27 of the switch; i.e., they are situated along the outer edges. The measurement bars are situated laterally outside the stationary part (coils 8) of the drive device. At least one of the measurement bars 6 has a bend.

This arrangement makes it possible to follow the position of a vehicle in the area of switch 2 a continuously, independent of the path that it takes. In every case, one of the marking magnets is continuously in the area of a measurement bar 6.

In the above-mentioned embodiments, measurement bars 6 are situated in the interior of the U-shaped sections of guide rods 4, which has the advantage that they are better shielded from magnetic fields of the drive mechanism. As already mentioned, and as can be seen in FIG. 5, guide magnets 14 are situated tangential to the measurement bars over the ends of the limbs of the U-shaped sections, which has the effect that their magnetic field lines in the sections are bundled, and the field is therefore very small in the area of the measurement bars. In contrast to this, as can be seen in FIG. 4, marking magnets 13 are situated radially to measurement bars 6, so that the field lines enter into the measurement bars, which results in the production of the above-mentioned ultrasound pulses. Due to the different arrangement of the marking and guide magnets 13 or 14, it can thus be achieved that guide magnets 14 produce significantly smaller signals than do marking magnets 13.

Measurement bars 6 can also be situated adjacent to guide rods 4, and can run along these; in this case, guide rods 4 are advantageously situated between coils 8 and measurement bars 6, so that measurement bars 6 are shielded as much as possible from the field of coils 8. It is also conceivable to situate measurement bars 6 at a greater distance from guide rods 4. In particular, the measurement bars can also be integrated in the area of, or in, coils 8. This is shown in FIG. 7, in which measurement bar 6 is situated in a recess in laminated core 8 a of coils 8. In this embodiment, the measurement bar is preferably also situated in a U-shaped section 4 a, so that disturbing magnetic fields are shielded.

While in the present application preferred embodiments of the present invention have been described, it is to be emphasized that the present invention is not limited to these, and can also be realized in other ways within the scope of the following claims. 

1. Rail system comprising a plurality of magnetostrictive sensors situated one after the other for measuring vehicle positions, each sensor shaving a measurement bar situated along the rail system and a measurement head, in order to detect the position of a marking magnet situated on a vehicle from a runtime delay, the measurement bars forming at least one measurement path that runs along the rail system, wherein the measurement path consists of measurement bars situated one after the other in non-overlapping fashion.
 2. Rail system according to claim 1, having a measurement control device that is fashioned in order to determine the position of vehicles having at least two marking magnets situated one after the other, exploiting the circumstance that when there is a transition from one measurement bar to the next measurement bar, at least one of the marking magnets is always effectively connected to at least one of the measurement bars.
 3. Rail system according to claim 1, having a multiplicity of rail elements situated one after the other, at least one measurement bar being situated in each rail element.
 4. Rail system according to claim 3, at least some of the measurement bars extending only over exactly one rail element, or at least some of the measurement bars each extending over a plurality of rail elements.
 5. Rail system according to claim 1, having at least one magnetizable guide rod for the magnetic guiding of the vehicles, the measurement bars being situated along the guide rod.
 6. Rail system according to claim 5, the guide rod having a U-shaped section, and the measurement bar being situated in the U-shaped section.
 7. Rail system according to claim 1, the coils being situated in the rail system as an active part of a linear drive mechanism, the measurement bars being situated at or in the active part of the linear drive mechanism.
 8. Rail system according to claim 1, the measurement bars being situated in a magnetizable U-shaped section.
 9. Switch for a rail system, in particular for a rail system according to claim 1, the switch having a first end, a second end, and a third end, the rail system branching from the first end into the second and third end, wherein the switch has magnetostrictive sensors for measuring vehicle positions, each sensor shaving a measurement bar and a measurement head in order to detect the position of a marking magnet situated on a vehicle from a runtime delay, a measurement bar extending from the first to the second end and from the first to the third end.
 10. Switch according to claim 9, at least a part of a drive device being situated in the switch, and the measurement bars being situated laterally outside the part of the drive device.
 11. Switch according to claim 9, the measurement bars being situated along the outer edges of the switch.
 12. Transport device comprising a rail system according to claim 1 and at least one rail vehicle, wherein the rail vehicle has at least two marking magnets that are effectively connected to the sensors.
 13. Transport device according to claim 12, the marking magnets being situated one after the other, seen in the direction of travel of the vehicle, in such a way that when there is a transition from one measurement bar to the next measurement bar, at least one of the marking magnets is always effectively connected to at least one of the measurement bars.
 14. Transport device according to claim 12 having a switch having a first end, a second end, and a third end, the rail system branching from the first end into the second and third end, wherein the switch has magnetostrictive sensors for measuring vehicle positions, each sensor having a measurement bar and a measurement head in order to detect the position of a marking magnet situated on a vehicle from a runtime delay, a measurement bar extending from the first to the second end and from the first to the third end, the vehicle having at least two marking magnets situated next to one another, such that when the switch is traveled through, at least one of the marking magnets is effectively connected to one of the measurement bars.
 15. Transport device according to claim 12, the rail system shaving at least one magnetizable guide rod, preferably having two parallel magnetic guide rods, the measurement bars being situated along the guide rod or rods, and guide magnets being situated on the vehicles that work together magnetically with the guide rods in order to guide the vehicles along the rail system.
 16. Transport device according to claim 15, the guide magnets having a different direction of polarization than do the marking magnets, and in particular the guide magnets being polarized essentially tangentially to the measurement bars, and the marking magnets being in particular polarized essentially radially thereto.
 17. Transport device according to claim 15, the guide magnets and the marking magnets being situated one after the other in one or two rows.
 18. Transport device according to claim 12, coils for a drive mechanism of the vehicle being situated in the rail system that interact with at least one drive magnet situated on the vehicle, a control unit being provided that determines in a control loop, via the magnetostrictive sensors, the position of the vehicle as a regulating variable, and controls the current through the coils as a manipulated variable.
 19. Method for measuring the position of a rail vehicle on a transport device, in particular on a transport device according to claim 12, the transport device comprising a rail system and at least one rail vehicle, the rail system having a plurality of magnetostrictive sensors situated one after the other for measuring vehicle positions, each sensor having a measurement bar along the rail system in order to detect, from a runtime delay, the position of a marking magnet situated on a vehicle, wherein the rail vehicle has at least two marking magnets that are effectively connected to the sensors and are situated one after the other in the direction of travel, and whose position can be measured using the sensors, the first marking magnet being used to determine the position of the rail vehicle if only a first of the marking magnets is situated in a predetermined measurement area of the sensors, and one or both of the marking magnets being used to determine the position of the rail vehicle if both marking magnets are situated in the predetermined measurement area of the sensors.
 20. Method according to claim 19, a front, in the travel direction of the rail vehicle, magnet being used to determine the position of the rail vehicle as long as its distance from a front, in the travel direction, end of the sensor is greater than a predetermined threshold value, and otherwise the rear, in the travel direction of the rail vehicle, marking magnet being used to determine the position of the rail vehicle until the front marking magnet enters into the measurement area of the next, in the travel direction, sensor. 